Balancing circuits



June 5, 1923.

' 1,457,336 HJA. AFFEL BALANCING CIRCUITS Filed sept. so, 1919 2sheets-sheet 2 /M 0 I l I I l Snl *und 20 #man 1Q' 3 u, y

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A OR EY HERMAN A. AFFEL, OF BROOKLYN, NEW YORK, AssIGNon To AMERICANTELEPON' AND TELECRAPH COMPANY, A coRronArroN or New YORK.;

iaAi-ANC'INGl CIRCUITS.

Application inea september4 so," 191e, serial Np.-327",4-5e.

To LIZ whom t may concer/lt Be it known that L' HERMAN A'. AFFEL,

residing at'BroOklyn, in the county of Kings and State of New, York',have in- 5 vented certain Improvements in Balancing Circuits, fication;kf ThisV invention relates to signaling circuits and more particularly toarrangements for translating low frequency signals into higher frequencycarrier currents and vice.

versa. Y.

In multiplex transmission systemsfemploying carrier currents it 1sVcustomary to Separate theeast and westchannels of a vcarriertransmission circuit in a manner similar to that employed in the casehofthe so-called 22 type telephone repeaters. A vcircuit of this typeinvolves balancing the carrier frequencies by means of an artificialline for simulating the main transmission lino at the carrierfrequencies. A low frequency balance is usually also provided ,in

f connection with the terminal signaling Cir- 25 cuit, to maintain theoppositely directed channels conjugate at low frequency. [Thetranslation of the ordinary-'signaling `frequencies into carrierfrequencies and Vice versa is carried out independently of thelbalancing circuit. In accordance with the present invention ,thefrequency ytranslation is madev an integral part of the balancingcircuit by locating the translatingdevice,y

' which may be either va modulator or .de

modulator, Vin the circuit .on either' side. of.

the point yof neutralization between the real and artificial line.Consequently the energy of an Outgoing transmission, for instance, whichit is desired to balance with refer 40 ence to the receiving channel,undergoes a,

change in frequency before the balance is effected. An arrangement ofthis character renders it possible to balancey the circuit' A withoutmaintaining a high degree of balance in ythe artificial line or networkfor both high frequency phase and magnitude, the fact that-the signalingfrequenciesbalanced are relatively low' obviating the necessity ofaccurate-phase balance in the high frequency Circuit i The invention maybe more fully under stood by reference to the followingj .de s criptionwhenk read in connection with the accompanying drawings Figures 1,2? .3`andy ofL which the following is a speci- Y 4. of which constitutelcircuit diagra "s fofdifferent embodiments ofthe iriver'itnjn.ft

ReferringtoFigure LMLfdesignatesamain transmission yline or rad-io'.antennacircuit Over which signals may be transmittedfby f means ofcarrier currents. Y-An articial 0U i line or'network provided forbalanc-4 ing the mainline with respect'to high frev`r quencies VTL'designates atrans Inittingr or sending circuit including a sourceofcarrierfrequency currents G and .a lreyLKg,V` The v source G may be ofanywell-known type,V

such as forinstancea Vacuum tube-oscillator. Thecircuit'TLisassociatedwith}tl1e;;

main line'ML andfthe balancing circuitfMN through abalancedtransformer[arrangeinentv comprising windings lQ'and 10', whichfa'rewound On separate cores. In order totranslate. carrier currents intolow? frequency 'sigan` naling currents, detectors Dxandly`r areineludedin the circuit of theffmain line ML l i and the balancing' Vline MN,loetween-ftheV points at which the two windings' l().;a'nd l0 of thetransformers `are included. inlthe.;`

.line and artificial line. Thesedetectorspor.

demodulators may be, of any well-known 90 e type, vSuch YOI IlSta-I'lceas vacuumtube rectif fying detectors.- A receiving' 'relay' Rywithreference toi-which the transmission circuiteftf- TL is to be balanced,is includedbetween lthe i lay R' will receive equal currentsandfno 95 feect will be produced uponthe sounder R.

It willvbeseenthat with this' construe- W tior i the-relay Ris'loalanced` `atflt'i'wid:'1- et-` quencies since the carrier"frequenciesare translated into low frequencies 'by means of 100 i thedetectors Dl and Djbefore "beingimpressed upon the .neutral point ofthe. oircuit to which 'the relay, R isf connected.l :Insp

order to control vtheinagnitude:0f the carrier lcurrents"'impressedupontle detectors 105f .l

and consequently'the magnitude OfthelOw i frequency signalingcur-'rents'w impressed uponvthe relay LR, Poisometers. -PyandfP-components of these carrier currents tending to iiow towards the relay Rare translated intov low frequency currents by means of the detectors Dand D and these low frequency currents balance each other with regard tothe relay R, so that the sounder R -isnot affected. High frequencycurrentsV received from the line ML. however, are

impressed upon thel detector D and upon be- .ing translated into lowfrequency currents flow through the right hand winding of the relay R toactuate the' same, so that the sounder R responds.

j Figure 2 illustrates the 'manner in which the arrangement of Figure 1maybe applied" for multiplex operation.

ML and MN designate the main line and artificial line, as

before, while TL designates a "common transmitting` circuitv which isassociated with transmitting circuits TNT2 and T3, said transmittingcircuits including lreys f K2, K2 and VK2, as well as the generators G1,G2 `and GR, respectively. The transmitting circuit TL is associated withthe line ML andthe artificial line `MN through a -b'alanced transformerarrangement '10i-i102 similar to that indicated in'Figure 1. Com-lmonreceiving citrus at RL and RL are associated with the main line andbalking included on either side ancing line MN, `respectively. Neutralor differential receiving relays R1, R2 and R.

are connected in bridged circuits between the'common'receiving circuitsRL and RL. Demodulators or detectors Dl yand D1 are included upon eitherside of the relay R, similar detectors D2-D2 and DfDi beof relays R2 andR12, respectively. VThe detectors 'D',D2 and Da are associated with thecommon circuitV RL ley-means of filters such as tuned circuits F1, F2and F3, which operate to select to each detector 'the proper carrierfrequency. Similar timed circuits F1, F2 and j ceiving circuit RL.

l through' the two windings 10 and 10 of the F3l serve to associate thedetectors D1', D.

n and D3 respectively, with the common re- Thedoperation is as follows:

actuation ofthe keys K1', K2 and K, to transl `mit, low frequencysignals, high frequency -carrier currents corresponding y to the fre--quencies o f the generators-G1, G2 and Gra` are supplied to the circuitTL andthe en ergy 4voff these frequencies `is transmitted respectivetransformers to the main line Upon the ML and the artificial line MN. Aportion of this energy is transmitted to the common receiving circuitsRL and RL and some of this energy may find its way through the selectingcircuits represented by tunedc1rcuits F F2, F3 and toa similar degreethrough tuned circuits F1, F2', F3 on the balancing side, beingsubsequently impressed on the respective detectors involved.

The carrier currents, upon being translated into low frequency signalingcurrents by the detectors, actuate equally the two windings of each ofthe receiving relays R1, R2

and R3, so that no resultant effect is produced. Received carrierfrequencies from the main line ML, however, upon entering f thereceiving circuit `RL, are selected by means of the filters F1, F2 andF3 and applied to the detectors D2, D2 and D3, with the consequentactuation of the right hand windings of the receiving relays R1, R2 andR3, so that the'low frequency signals actuate said relay.

Figure 3 illustrates the manner in which the principle of the inventionmay be applied to a carrier channel for the transmis-V sion of telephonecurrents. In this case the transmitting channel TL;l includes amodulator M which may be of any type, but is preferably a duplex vacuumtube modulator of the type illustrated in the U. S. Patent to John R.Carson, No. 1,343,307, of June 15', 1920. Carrier currents of the properfrequency are supplied to this modulator from a suitable generator G,over a circuit 20. The receiving channel RL1 is connected to neutralpoints between the main line ML and vthe artificial line MN, while thetransmitting channel TL1 is associated with said main line ML andartificial line MN through a*y balanced transformer arrangement, thetwo" halves 10 and 10 of which are included in the mainline andartificial line circuits respectively, on either side of the neutralpoint. Demodulators or detectors D1 and D1 are included in the main linecircuit ML' and the artificial line circuit MN on either side of theneutral connection of the receiving .channel RL1 and between thepointsat which the two windings of the balancing transformers areconnected. These demodu lators or detectors may be of any well-knowntype, but are preferably duplex vacuum tube detectors of the typeillustrated and described in the U. S. Patent to John R.

-circuit21 from the generator G1 or another :separate generator. Inorder that the phase :angle of the carrier currents supplied to the-detectors D1 and D1 be controlled, a

120. i Carson, No. 1,343,308 of J une 15, 1920. As the phase adjustingnetwork schematically Vindicated at X may be included in .the carriersupply circuit of one of the demodulators,

as for instance D1;` This networl; may be ofl any wellknown charactersuch .as ya iietwork including adjustable capacity and inductance forchanging the phase angle."

The operation is 'as follows: Telephone currents incoming from thecii'cuit- TLl modulate carrier currents from the 'source Gl,"by meansofthe modulator M1 and are supplied through the transformer sections l0and l0 of the main line ML and MN, respectively. The' components `of theresultvant modulated lcarrier current energy'iinpressed upon thedetectors l), and D1 cause equal and opposite' low frequency telephoniecurrents to iiow to the neutral points 22 and 23 of the circuit, so thatno current flows lto the receiving channel RLI. lvlodulatedcarriercurrents receive-d in the zline L1, however,

arel impressed upon the detector vD, and' translated into low frequencytelephone c urrents, which not being balanced by equal and i oppositecurrents from the detector D1", flow to the receiving channel RLl.

Figure et shows an arrangement in which the modulating element may beincluded'in the balancing circuit, instead of the deinodu- 'neutralpoints 22 and 23 and are supplied with carrier currents from the sourceG1 over a circuit 20. The phase adjusting element X may be included inthesupply circuit of one of the modulators, as for instance themodulator M1. Low frequency signaling currents incoming from thecircuit'TL1 are applied to the neutral points 22 and 23 of the circuitand flow in opposite directions :to the modulators M1 and M1. By meansof the two modulators the low frequency currents are translated intocarrier currents which are transmitted to the line ML and Mil,respectively. These carrier currents produce opposite reactions upon thereceiving circuit RL, and are therefore balanced out with respect tothis circuit. Carrier currents incoming from the vmain line ML aretransmitted through the transformer element kl() to the receivingchannel BL1. and after being detected by the detector Dlfand therebytranslated into low frequency telephone currents, are transmitted to thereceiving apparatus (not shown).

, tandem between said transmission 'circuiti-l king signals originating'withsaid sending`rxvv signaling circuit into high frecpiency.cur`

It will be'obvious lthat the generall principles herein disclosed may beAembodied in many other organizations widely different` from thoseillustrated,` without departing from the spirit of the inventionasydeiiiied lin? the following claims. y 'l lVhat is claiinedris;r i v 1In asignaling system, a transmission circuit, a sending circuit',v areceivingy circuit, a balancing .circuit for, balancing said trans-jl.mission circuit, wherebysaid sendingand re- 'ceiving circuits maybe made'substantially conjugate, means for translatingl signals originating insaid sending-'circuit into high frequency currents7 -,mea iisi for`translating'BO received high frequency currents vintov lowfrequencysignaling currents .1to1 be trans.y mitted -oversaidreceivin'gfcircuit, oiie'of said 'translating meaiiszbeing includedinand said balancingcircuit indep'endentlyof the corresponding'signalingcircuit', sothat i the energyto be balanced undergoes a change offrequency lbefore thebalance is effected.

2. In al signaling systemya transmissioni-9.0

circuit, a pair of *signalingYL circuits, ione for sending .andone forreceiving., a balancing icircuit for rendering said signaling circuitssubstantially conjugate, means yfor'tran'slaftrents, and means fortranslating receivedy high frequency currents into. low frequencysignaling ycurrents for transmission' over 'said`receiving,signaling`circiiit,rone of said trans-@,100

latiiig vmeans beingincluded in tandemfbetween said transmission circuitand said balancing circuit independently of they corresponding signalingcircuit whereby the ener-gy which it is desired to balance undery'goes achange of frequencybefore balance is effected, the other translatinglmeans being A included directly in' the corresponding signalingcircuit.

3. ln a signalingf'system, a transmission 110 circuit, a pair ofsignaling "circuits, one for sending and one for receiving, a balancingcircuit for rendering-said signaling circuits substantially conjugatewith Yrespect to each other, lone of said signaling circuits being'as-vv11.5

sociated with said transmission` circuit and balancing circuit atapointbetween `said two last mentioned circuits, lme ansl for translatingsignals originating with the sending signaling circuit into highfrequency carrier currents, means for translating .received carriercurrents yintolow frequency signals for transmission'over the receivingsignaling circuit, one of said translating means being arranged induplicate,.with the duplicate elements onr1'25 either side of the pointat which one of said signaling circuits is associated withsaid ytransmission circuit and balancing circuit,A

the other signaling circuitY being associatedv with saidtransmissioncircuit and balancing circuit at pointsA in said two lastmentioned circuits beyond the points of their connection with saidduplicate translating means.

4. In a signaling system, a transmission circuit, a pair of signalingcircuits, one for sending and one for receiving, a balancing circuit forrendering said'signaling circuits substantially conjugate with respectto each other, one of said signaling circuits being associated with saidtransmission circuit and balancing circuit at a point between said twolast mentioned circuits, means for translating signals originating withthe sending sig naling circuit into high frequency carrier currents,means for translating received carrier currents into low. frequencysignals for transmission over the receiving signaling oircuit, one ofsaid translating means being arranged in duplicate, with the duplicateelements on either side of the point at which one of said signalingcircuits is associated with said transmission circuit `and balancingcircuit, the other signaling circuit being associated with saidtransmission circuit ant balancing circuit at points in said two lastmentioned circuits beyond the points of their connection with saidduplica-te translating means, the other translating means being includedin said last mentioned signaling circuit.

tvvo last mentioned circuits, means for translating carrier currentsinto low frequency signaling currents arranged on either side of saidpoint in said transmission and balancing circuits respectively, asending circuit associated with said transmission and balancing circuitsin said two last mentioned circuits beyond the points of theirconnection with said translating means, and means to translate lowfrequency signals originating in said sendingcircuit into high frequencycarrier currents.

6. In a signaling system, a transmission circuit, a balancing circuit, aplurality of receiving means associated with said transmission andbalancing circuits at a point intermediate said two last mentionedcircuits, means for translating high frequency carrier currents into lowfrequency signaling currents to be transmitted to said receiving means,said translating means be- ,I

ing arranged in duplicate and associated with said transmission andbalancing cir` cuits respectively on either side of said receivingmeans, a sending circuit associated with said transmission and balancingcircuits at points in said two last mentioned circuits beyond the pointsof their connection with said translating means, a plurality of sendingmeans associated with said sending circuit, and means for translatinglow frequency signals originated by said sending means into highfrequency carrier currents.

ln testimony whereof, I have signed my name to this specification this29th day of September, 1919.

HERMAN A. AFFEL.

